1. Field of the Invention
This invention relates generally to structures for sensors that incorporate pivot functions, and more particularly to micro sensors that incorporate pivot functions, and have flexural pivot structures with equal and opposite senses of stress on a single surface.
2. Description of the Related Art
In electromechanical transducers, a transducing element is utilized for detecting the relative displacement of two parts and for developing a corresponding electric signal. Generally, such relative displacements have been measured in the past with various kinds of strain gauges. However, these have a tendency to be of considerable weight, some of which are very bulky, some of which are not very sensitive. Those that are have intricate designs which are very expensive. As mentioned above, the present invention is directed to a force-type sensor or gauge which is mounted between two parts between which a force is applied. The gauge is, therefore, strained in an amount which depends upon that force. It is substantially smaller than prior art force gauges, is relatively simple in structure, is easily manufactured, and is, therefore, less expensive.
As such piezoresistive transducers have developed in use over the years, it has become increasingly desirable to have extremely small sensors of high sensitivity and low bulk. However, in order to develop force gauges which are of extremely small size, difficulties arise in the handling thereof for subsequent mounting upon their substrate, once they are developed. They are difficult to handle not only because of their small size, but also because of their fragility.
One of the primary advantages of force transducers lies in the fact that the displacement between the pads at each end thereof produced by relative motion of the two parts to which the pads are attached is concentrated in the “suspended”, so to speak, portion of the force gauge which can mechanically amplify the strain being sensed or measured. Furthermore, the resistance change of the element per unit displacement is greatest as the length of the element is reduced. By use of both short gauge lengths and appropriate leverage very large resistance changes may result from very small displacements. This change in resistance is determined by means of electrical current flowing through the element from one pad to the other, and measuring changes in voltage or other electrical properties resulting from changes in resistance. However, when attempts are made to reduce to a smaller size such force gauges difficulties arise relative to the handling thereof in mounting upon their substrates, as well as other problems which ordinarily arise in handling very small objects.